A new portable water cooled rotating anode X-ray tube will be designed and built in a configuration particularly suited to the needs of the X- ray crystallographer: e.g., four useful windows, zero to ten degrees take-off-angle, copper target, convenient size, weight, and requiring only high voltage, water, and low voltage lines to connect it to a remote power supply. The tube is baked-out at manufacture and sealed off at vacuum levels appreciably lower than achievable on any existing crystallographic rotating anode unit. It uses a combination of special bearing configuration and integral ion pumps to maintain the vacuum during use. This assures improved shelf life, filament life, reliability, and performance. Special attention will be directed toward achieving a very small X-ray source (0.1 X 0.1mm projected) which (1) reduces the size of the diffracted spot, (2) provides increased brilliance thereby improving peak to background ratios, (3) permits the examination of crystals having larger unit cells, etc. All of these are extremely important in the structure analysis of proteins, of other large molecules and of crystals that re extremely small themselves. This new portable source will open a new horizon in the study of liquids.